Plotting square



April 5,1927. 7 4

F. HOLLAND momma SQUARE Filed Sept. 9 1925 NFQMF:

N. N m m \N k m m m H h N M Mai/17021404 INVENTOR.

. ATTORNEY.

on the sides of the member 1. The scale on the side 15 of the member 2 is indicated at 17, and the scale on the side 16 of said member 2 is indicated at 18.

The member 2 consists of a dove-tail head 19 of a thickness corresponding to the depth of the groove 7, and said member 2 further includes a substantially elongated body portion 20 of greater thickness than the thickness of the member 1, and said body portion 20 is formed with the bevelled sides 15 and 16 and the scales 17 and 18. The inner end of the body portion 20 is bevelled, as at 21, and snugly engages the bevelled side 4 of the member 1. The body portion 20 is connected to the head 19 by a coupling portion 22 which seats on the upper face of the member 1 and extends transversely of, as well as being formed integral wit-h the head 19. The body portion 20 and coupling portion 22 are of the same width and of a width materially less than the length of the head 19, and said coupling portion 22 is disposed centrally with respect to the head 19 and has its rear end bevelled, as at 23 and with the bevel forming a continuation of the bevelled rear side of the head 19. The coupling portion 22 terminates in the body portion 20 at the upper part of the rear end thereof. The lower face of the coupling portion 22, at its forward end, terminates in the upper end of the bevel at the inner end of the body portion 20, and the forward side of the head 19 terminates in the lower face of the coupling portion 22. The bevel at the inner end of the body portion 20 extends in a plane parallel to the planes of the opposing wall of the groove 7 and the adjacent side of the head 19. The lower face of the body portion 20 is flush with the lower face of the member 1 and the bevel at the inner end of the body portion 20 is of the same height as the height of the member 1.

The adjustable member 2 is termed a plotting arm and the connection between the inner end of said arm and the stationary member 1 permits of the arm to slide throughout the length of said member 1 and also to position the arm at an angle of 90 relative to said member 1. The plotting arm can be moved the entire length of the stationary arm for the purpose of coordinating any part of the scale on the member 1 with the plotting edge of the arm.

The manner of using the plotting square in accordance with this invention is as follows i The instrument is placed on the plotting paper with the lower horizontal scale of the base scale at a line representing the height of instrument and with the center zero of the base scale on a point corresponding to the center line. The retaining members are then adjusted in order to prevent slipping of instrument on the pa er. The plotting arm is then moved to right or left as required by the indications of the survey or field notes to a point on the scale corresponding to the horizontal ground distance of the reading. With the plotting arm thus in position, the rod reading is plotted direct at a point on the scale on the working edge of the plotting arm corresponding to the rod reading. The plotting is done by placing dots at the proper position and later, when the series have been plotted, connecting the dots by drawing lines from one to the next. The operation of the instrun'icnt is with the plotting arm pointing toward the operator, unless plus rod readings are being considered, in which case the plotting arm should point away from the operator. This is the operation in plotting from cross section and profile survey or field notes.

In plotting from topographical survey or lield notes the lower edge of the base scale is placed so as to represent the base line. Horizontal ground distances are determined on the scale on the lower edge of base scale while features and objects found either to right or left of the base line are plotted by using the plotting arm as before described.

In plotting curves, place the middle zero on base scale at a point corresponding to the point of intersection, move the plotting arm along the base scale until the working edge is at the number which corresponds to the tangent distance. Then plot the radius of curve on the plotting arm. This gives the radial point of the curve. Many other uses are claimed for this invention such as for measuring angles as by the use of the steel square, use as a T square, use as a scale.

The instrument is a novel and useful article of manufacture as it does away with the line counting on the plotting paper which counting is the cause of many errors and much detailed work. Furthermore, it

is collapsible and portable, being intended to be a part of the field equipment of any engineer or surveyor.

It is to be understood that the construction of the device is not limited to any material or composition of materials that may enter into its manufacture, nor to any particular sets of scales or graduations on the invention as described herein. The essence of this invention being the novelty and usefulness of the arrangement of parts and scales, as well as the simplicity and portability of the manufactured invention.

What I claim is 1. A plotting square comprising a combined plotting arm carrier and base scale member having its upper face, centrally thereof, provided with a lengthwise disposed dove-tail groove extending from one end to the other end of said member, and a plotting arm scaled to conform to t e s al f i member and provided with a dove-tail head slidably mounted in said groove for maintaining the arm at right angles to said member, said arm having its inner end edge overlapping and snugly engaging said member, and retaining members threadedly engaging with said combined carrier and base scale member for detachably securing it to a support to prevent the slipping thereof, said retaining members arranged below said head having their tops flush with the bottom of said groove and extending through and projecting from the lower portion of the combined carrier and base scale member.

2. A plotting square comprisinga grooved plotting arm carrier and base scale member, an adjustable plotting arm scaled to conform to the scale of said member and provided with means seated insaid groove for slidably connecting the arm to said member at right angles with respect thereto, a plurality of disks mounted in said member and having the upper faces thereof flush with the base of the groove thereof and each formed with an opening having a threaded wall, and retaining members each including a head and a tapered shank, said head threadedly engaging with the walls of said openings and said shank projecting from said member and engaging in a support for retaining the member in non-slipping position.

3. A plotting square comprising a combined plotting arm carrier and base scale member having beveled sides and a lengthwise disposed centrally arranged dove-tail groove extending from one end to the other end of its upper face, a plotting arm including a body portion having beveled sides, both scaled to conform to the scale of said member, said arms further including a dove tail head slidably mounted in said groove and a coupling portion connecting the upper part of the inner end of said body portion to said head, said body portion having a beveled inner end edge snugly engaging throughout and overlapping one of the beveled sides of said member, and said coupling portion seated on said member. In testimony whereof, I aifix my signature hereto.

FRANK HOLLAND. 

